Welcome to our resource for MG Car Information.



TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Too lean

70 TR6, relatively new addition to our family.
Working on setting up carbs. Seem to have them
pretty well in sync, but having trouble adjusting
mixture. Pretty smooth idle 850-900, seems to run fine.
However when using the lift the carb piston method the
motor wants to quit. If I've done my homework this would be indicative of too lean a mix. Both carbs diplay same symptom. No amount of enriching (clockwise on the ZS, right?) seems to remedy this. Any ideas?
Ian Kinaid

After spending some time reviewing older posts, think I now have some ideas where to start. Guess I should have started with the Timing survey : )
Ian Kinaid

OK, now I'm frustrated.
Checked timing, set to about 15/16 BTDC idles fine
after warmup at 850.
Just can't get the mix set. lifting the piston still
would indicate lean. Ran it all the way clockwise
resulted in no discernable change. Checked for leaks couldn't find any. same for both carbs. What's most
interesting is the darn thing seems to run seemingly
well despite all the adjustments I make.
Bugger $#@%@
Ian Kinaid

Hi Ian,

I am also kind of new to 6s, and there are definitely more competent mechanics on this BBS than me, but until they pipe up, here are a couple of thoughts...

Have you checked your fuel line? I.e. is there enough pressure from the fuel pump, and are your fuel filter and lines clear? The fuel filter is a pretty cheap, easy thing to replace, especially if you do not know how long that puppy has been in there. Get ready for tons of gas leaks from both the in & out lines when you change this.

Was 15/16 BTDC with the vacuum retard disconnected from the distributor? By the book, it should be at 4 ATDC with retard connected, and 12 ATDC without. So 15/16 is probably where most people on this BBS would recommend, and maybe push this a bit higher till you get pinking. Mine are set to ~16 ATDC right now. I will play with this more after I rebuild my carbs.

...good luck,



Hey Ian

I have the same problem with setting the mixture as you do. I understand in principal about the lifting of the piston but it always stalls my car no matter which way I turn the adjustment. As with Lucas...Price of Darkness, is Stomberg, King of Stumbling??

Thanks guys.
I'm satisfied with the timing, and think I have the carbs in sync. I'll have to check the fuel lines, don't think that's the problem though. I'm going to try the colortune device now. I'll post how that goes. : )
Ian Kinaid

Ian--Welcome to the finicky world of ZS carburetion. I suggest you get some carb cleaner spray and, with the engine idling, spray at all vacuum leak points. I'd focus on the four seals on both ends of the carb throttle shafts first. That's where my leaks were occurring and it's easy to renew those seals (although you have to remove the carbs). If there's a vacuum leak, the idle will drop when hit with the cleaner.

Good luck and let us know how it turns out.

Rick O.
Rick Orthen

Hello Ian,
Spark plug readings are a good indicator of whether you car is rich or lean(any manual or a bit of surfing on the web will describe how to do this check). You might want to check your plugs now whereever your car is sitting to get a general idea of how it is running. But a "plug cut" or "plug chop" is the best way to get a good reading - you can do this after a good hard drive at higher rpm at highway speeds (which is where cylinder pressure and lean conditions would show)- you should stop somewhere where you can check the plugs without having to travel far at low rpms - this will give you a more accurate reading without the reading being fouled by lots of low speed and possibly rich running.
Hope that helps!

This thread was discussed between 07/05/2002 and 09/05/2002

Triumph TR6 index